Apparatus to facilitate instruction in mathematics



Dec. 15, 1931. H. w. CHESHAM Filed Jan. 2, 1951 I Patented Dec. 15, 1931UNITED sT r s HENRY WILLIAM CHESHAM, OF SHEFFIELD, ENGLAND APPARATUS TOFACILITAIE, INSTRUCTION IN MATHEMATICS Application filed January 2,1931, Serial No. 505,260, and in Great Britain January 4, 1930.

This invention relates to apparatus to facilitate instruction inmathematics, of the type comprising a disc having a radial slit and asecond disc having a radial slit therein so that the slit edge of onedisc canpassaddition to the mathematical representation. 7

Each disc has a circularly directed slot at the end of the radial slit.One disc is convenient- 1y mounted on a sleeve fixed in relation to theother disc, and one or both discs is or are provided with a hand grip orsupport at the centre of the disc.

Referring to the drawings Figure 1 is a front view of a deviceconstructed according to this invention.

Figure 2 is a section on the line aa of Figure 1.

Figure 3 is a back view. Figure 4 is a perspective View of a discdetached.

Figure 5 is a sectional elevation of the centre portions of the disc andmounting sleeve detached, and

Figure 6 shows the apparatus arranged with the disc in a horizontalposition. A The index member is conveniently a disc 1 which has a radialslit 2 extending from the circumference to the centre. A second disc 3having a similar radial slit therein is located at the side thereof andthe index member 1 is rotatably mounted in relation thereto. The indexdisc may be stationary and the cover disc movable. The slits are suchthat one slit edge of the index disc can be passed. through the slit inthe cover disc and rotated so that a part, or the Whole of the coverdisc, can overlap the index disc, or viceversa. The index disc and coverdisc are preferably formed of bakelite or a metal of light weight, andin order that the disc will readily pass through the slit in the otherdisc a circularly directed slot 4 passes from the inner end ofthe radialslot in each disc, one slot 4 in one disc passing in one direction,whilstthe slot 4 in the other disc passes in the other direction. Thediscs are rotatably mounted. conveniently by means of a sleeve 5, fixedor formed centrally to one disc 3 on which the other disc 1 is rotatablymounted.

A flange 6 on the other face of the disc, at the centre andinside theslot 1, is provided for the holding and manipulation purposes. 0 Theother disc 2- has a finger grip 7 similarly fixed to the outer face, andsuch disc is prevented from axial movement on the sleeve 5,

by means of plug sleeve 8 or the like. The two discs 1 and 3 areslightly sprung in use to lie close together and interfitted with a partof one located behind the other and the rest in front of the other asshown by Figure 2.

The front side of the index plate 1 may be graduated in degrees. so thatangles may be readily visualized. The back of the member 3 is, in oneinstance, divided into ten sections and each section is divided into twodivisions and the divisions divided into five subdivisions, so thateither side of the apparatus may be utilized. With the disc thusgraduated decimals can be readily taught, as for instance, it can bereadily seen that .25 represents'a quarter of the whole disc andconsequently each individual quantity can be actually visualized,thereby enabling the student toniuch more readily grasp the meaning ofthe mathematical quantities. The instrument" thus constructed may alsobe utils. ized'by the instructor as a protractor for blackboard and likedrawing; the aforementioned sleeve pivotall'y connecting the two discsenables a point on the blackboard to be viewed therethrough andconsequently en- 91') abling the device to be placed concentrically inrelation to such point.

The aforementioned device can also be utilizedfor giving instruction insurveying. For this purpose a stand 9 is provided which 95 convenientlyhas a bearing at its upper end, and a fitting 10 is provided, one end 11of which is formed as a plug for fitting into the aforementioned sleeve8, whilst the other end 12 is adapted to engage onthe top of the stand9; A sight tube 13 may be detachably fixed in holes ,in the finger piece7. The top of the stand may be conical and the fitting 1O bears on thisconical portion to be rotatably held thereby. In this position the indexplate is held in a vertical position and can therefore be utilized forobtaining angles, a plumb line or spirit level placed on the sightingtube enabling the horizon to be obtained, The end of the fitting 11 canalso engage the stand 9 as shown in Figure 6, so that the disc graduatedin degrees is held in a horizontal position to enable horizontal anglesto be obt ined. The stand 9 may be fixed on a tripod.

The three separate parts shown by Figure 5 may be formed as singlebakelite mouldings or may be built up from individual mouldings. Thedevice may, however, be made from any suitable material. The devicecomprising the index disc and the cover disc may also be made in a smallsize for use by the individual student, in which case the we discs maybe pivoted together by means of a ferrule.

Claims:

1. Apparatus to facilitate instruction in mathematics, comprising a dischaving a radial slit therein and a circularly directed slot at thebottomof the slit passing in one direction, a cover disc having a radial slitand a circularly directed slot at the bottom of the slit passing in theother direction so that the material of the discs on the outer sides ofthe slots can flex laterally and so that the slit edge of one disc canpass through the slit in the other disc, and means for rotatablymounting the discs in relation to one another.

2. Apparatus to facilitate instruction in mathematics, comprising a dischaving a radial slit therein and a circularly directed slot at thebottom of the slit passing in one direction, a cover disc having aradial slit therein and a circularly directed slot at the bottom of theslit passing in the other direc tion so that the material of the discson the outer sides of the slots can flex laterally and so that the slitedge of one disc can pass through the slit in the other disc, andbearing members carried by the said discs inside the said circularlydirected slots.

3. Apparatus to facilitate instruction in mathematics, comprising anindex disc having a radial slit therein and a circularly directed slotat the bottom of the slit passing in one direction and provided with avscale on one or both faces, a cover disc having a radial slit thereinand acircularly directed slot at the bottom of the slit passing in theother direction so that the material of the discs on the outer sides ofthe slots can flex laterally and so that the slit edge of one disc canpass through the slit in the other disc, means for rotata-bly mountingthe discs in tion so that the material of the discs on the outer sidesof the slots can flex laterally and so that the slit edge of one disccan pass through the slit in the other disc, a sleeve fixed centrally onone disc, and means for fixing the other disc on the sleeve to berotatably mounted thereon, and hand grips carried centrally on the outerface of each disc.

5. Apparatus to facilitate instruction in mathematics, comprising anindex disc having a radial slit therein and a circularly directed slotat the bottom of the slit passing in one direction, a cover disc havinga slit therein and a circularly directed slot at the bottom of the slitpassing in the other direction so that the material of the discs on theouter sides of the slots can flex laterally and so that the slit edge ofone disc can pass through the slit in the other disc, a sleeve fixedcentrally on one disc, and means for fixing the other disc on the sleeveto be rotatably mounted thereon, and a-stand for fixing the said sleevethereon.

In witness whereof I have signed this specification at Sheflield,England.

HENRY WILLIAM CHESHAM.

